Conventional techniques for daytime detection and identification of ships in open water are human intensive. One such technique simply includes the visual inspection of aerial photographs by a live human being. Since the ships themselves typically appear as small dots in the photographs, the human photograph inspectors often search for telltale signs of a ship, such as their wakes. Not only is this technique labor intensive, but the vastness of the open oceans renders this technique limiting. Only so many square miles of open ocean photographs can be visually inspected by a human being (or even a group of human beings) in a reasonable period of time, before the photographs become stale (i.e., any spotted vessel will have long since departed from the photographed region).
Another conventional technique is the use of radar. However, radar is limited in its range by the curvature of the earth and typically cannot extend much past the horizon. Again, use of radar to detect and identify a ship in open waters still requires active monitoring by a human operator.